Durable Flooring

Recovery From Indentations

Armstrong’s durable and resilient LVT and Vinyl sheet floors are perfect for high impact and high traffic applications. These
floors can be used in a number of spaces including office lobbies, retail stores, and even gyms. Explore all of our hard-wearing
floors to find the solution that’s best for your project.

Okay, this is an example of an indentation machine. Some of which were actually developed right here in Armstrong over 45 years ago. They're designed to evaluate a resilient product's resistance to and/or recovery from indentations. Every resilient flooring specification does have at least one requirement, if not two requirements for indentation resistance. Now, there's different types of indentation resistance. There's short term resistance, which would be from impact loads from foot falls, high heels, maybe somebody sitting on a chair for a short period of time. And then there's longer term whereas what we refer to as Static Load Limit or Static Load Resistance which is typically gonna be much longer term - shorter loads or smaller loads for longer periods of time. Now, each flooring specification, because they're written for individual products, it might be VCT, solid vinyl tile, homogeneous rubber, linoleum, whatever. Each one of those will determine the parameters by which the test is to be run. Now, in the case of VCT, we're more interested in resistance to indentation, than we are recovery. VCT tends to be very hard, and if the tile is too hard, it's going to be prone to breaking or cracking when it's installed. If it's too soft, it's going to be susceptible to indentation. So, there's kind of a slot that you have to hit when you're evaluating vinyl composition tile. The ASTM specifications, and I should mention this is this is an ASTM standard test method. The ASTM specification for VCT requires that the initial indentation be no less than 6 thousandths of an inch, and no greater than 15 thousandths of an inch. So, there's that kind of slot or sweet spot that you want to hit, so you can balance or optimize performance properties. On sheet products, which tend to be more highly plasticized, more flexible and softer, we're more concerned about those product's ability to recover from indent, or what we call residual indentation. And again, the specification or the particular type of product will drive the parameters of the test. By that I mean, what type of foot, or indenter foot, is inserted in the machine? Is it a flat foot or is it a hemispherical foot? Is it a small diameter or a large diameter? The test method will also specify, the load that will be applied to that indenter foot when it's installed in the machine. And it will also tell you what dwell the time is. A dwell time is the amount of time, that the load will actually be applied to the floor. And, there's also, for some tests, what we call a recovery period. After the load's removed, typically that's about 60 minutes, the recovery period, the sample is allowed to recover. After which, they'll go measure for residual indentation, and the test is really quite simple. The flooring sample is installed in the machine, with the appropriate foot, the lab technician will take the initial thickness, or the initial reading on the flooring sample. The load is then applied directly to the foot from the appropriate amount of time. When the timer goes off, whether it's one minute, five minutes, 15 minutes or even 24 hours in, in the case of longer term static loads, they will take the initial indentation after the time period and then take the load off of the sample. And in a case of residual indentation, the sample will be allowed to recover for 60 minutes, and then they'll remeasure the thickness of the product and calculate the residual indentation.